Mantle influence of syn- to late-Grenvillian alkaline magmatism in the Grenville Province: causes and implications
Bibliographic record
Abstract
Several features of Geon 10 magmatic evolution in the Grenville Orogenic Belt is difficult to reconcile with generally accepted models of protracted (ca. 100 Myr) continent–continent collision during the Grenville Orogeny. Particularly the presence of (partly) mantle-derived magmatic rocks, some with subduction signatures, intruded during the inferred climax of the orogeny, is not well accounted for in existing models. We present new geochemical, Lu–Hf isotopic and U–Pb geochronological data from three alkaline composite plutons in Quebec, Canada, that give important clues to the tectono-magmatic evolution from ca. 1040 to 1000 Ma of the Grenville Laurentian margin. The oldest pluton, emplaced at ca. 1038 Ma, has a geochemical composition compatible with derivation in an arc setting by partial melting of subcontinental lithospheric mantle. The two youngest plutons, emplaced at ca. 1014 and 1009 Ma, respectively, have typical within-plate geochemical signatures showing no obvious influence of subduction. The new and existing data indicate that much of the Grenville Laurentian margin experienced ensialic magmatism through large parts of Geon 10, an observation calling for alternative models to the existing to explain the Geon 10 evolution of the Grenville Orogenic Belt. We propose a model where Ottawan metamorphism and magmatism resulted from accretion of terranes and continued subduction beneath Laurentia until late Geon 10. Late Geon 10 magmatism could have been related to slab breakoff prior to or at the onset of a late Geon 10 collisional event, which has also been recently proposed based on paleomagnetic arguments.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".